Stephen Hawking - light cones

They're the ones that aren't heavy. You use the heavy ones for marking out roadworks - the light ones get blown away as soon as the wind gets up. Light ones are useful for things like holding ice cream. Hope that clears it up.

Light cones are actually the graph plotted between time axis & the volme or distance/area covered by the light while originating from a point presently in the present i.e. at time axis 0. The reverse cone denote the past & the upward cone represents the future.This is just a brief idea about the light cones.If u want in detail then do let me know